SoCal Jet Boats

I was going along about 4,000 rpmís on the CT River the driveline went out. No warning. Iíve had 3 or 4 other instances with universals binding and blowing apart with my 20í Aluminum Gator jet. This is a SD309 AT pump powered by a vortec 350. Geometry looks fine. I grease them a couple times a year, doesnít seem to matter. I get about 100 hours on them and they go. This is the first time the frame of the driveline has cracked apart, the other times it was just the universal joints. I have a refreshed one (pictured) to install. It isnít super hard to fix, but itís annoying that it keeps happening.

With a jet boat you're connecting two fixed points with a joint that has no tolerance for longitudinal mis-alignment. The engine and pump don't have to be perfectly parallel, but the centerline of the crank and the centerline of the pump must intersect at the center of that double cardan joint. The way the case of that DC joint came apart, I'm pretty confident it's an alignment issue. I know I'm new to this forum, but I've been working on all kinds of shaft driven industrial equipment,farm equip, well heads etc. for almost 40 years and that looks like alignment to me. It's too bad somebody hasn't adapted a Dodge coupler (nothing to do with the auto maker) to a jet boat. They're perfect for imperfect alignment applications and absolutely constant velocity. BlackSheep-- I was reading about your boat/engine build on another thread. Love it! I have built a couple hi-perf 460's over the years and am a fan of those (385 family) engines. With a set of cleaned-up (exh port) D3 heads and about 10:1's you can build a real torque monster.